The script has been published in 2 different out-of-print editions:
1. Samuel French used to own the rights to the show, and as you probably know, SF sells copies of all their scripts without you having to aquire the rights, etc. so you can search through used book sites (ebay, abe, the used section of b&n) and try to find that one.
2. There was a published hardback edition of the script published as well. Its a little bit more rare and probably more expensive, but for a collector or someone who loves the show its a great thing to have.